Microbiology 4 - Respiratory tract infection Flashcards
What is the most likely causative organism in a young patient with a lower lobe pneumonia, raised WCC and CRP?
Strep pneumoniae
Recall the appearance of streptococcus in culture
Gram positive cocci in chains
Recall how streptococcus pnuemoniae is identified in the lab
Demonstrates alpha haemolysis
alpha haemolysis: strep pnuemoniae (optochin sensitive), strep viridans (not optochin sensitive)
beta haemolysis: GAS (Bacitracin sensitive), GBS (Not bacitracin sensitive)
What is the most common pathogen implicated in CAP?
Streptococcus
Is streptococcus gram pos or gram neg?
Gram pos
Recall the 2 pathogens that can cause typical CAP
S. pneumonia
H influenzae
Which investigation are indicated in suspected CAP?
FBC, U&E, CRP, LFT
Blood cultures, sputum MC&S
What severity score can be used to score CAP?
CURB-65 Confusion Urea (>7) RR (>30) BP (<90 systolic) >65 years Score 2 or above = admit
What is bronchitis?
Inflammation of medium sized airways
How does bronchitis appear on CXR?
Normal
How do haemophilus influenzae appear under the microscope?
Gram neg cocco-bacilli
On what sort of agar should H influenzae be cultured?
Chocolate agar
What colour sputum is produced in Strep pneumoniae?
Rusty
Kelbsiella: red colour
psuedomonas, H.influenzae: green colour
Which type of atypical pneumonia is associated with hyponatraemia?
Legionella
What is the special culture required for legionella?
Buffered charcoal yeast
What extrapulmonary features are likely in atypical pneumonia?
Hepatitis
Hyponatraemia
Which type of pneumonia is associated with confusion, abdo pain and diarrhoea?
Legionella
Which type of pneumonia is spread by birds?
Chlamydia psittaci
What is an empyema?
A collection of pus in the pleural cavity, gram-positive, or cultured from the pleural fluid
What are the key features of TB pneumonia?
Ethnicity Prolonged prodrome Fevers Weight loss haemoptysis
Recall 2 stains that can identify TB
Auramine(auramine-rhodamine) stain
Ziehl-Neelsen stain
Both of these are acid-fact bacilli testing stains
How can upper and lower respiratory flora be differentiated?
Bronchial lavage
Which type of pneumonia is common in the immunosuppressed (eg people who have had TB, HIV)?
Pneumocystis jirovecii
Recall 4 symptoms of pneumocystis pneumonia
Dry cough
Weight loss
SOB (exertional dyspanea- after walking like 10m)
Malaise
treat with co-trimoxazole
Recall the typical CXR finding in pneumocystis pneumonia
Bat wing
What is the most likely cause of pneumonia when there are interstitial changes on CT, neutropaenia and a history of ABx treatment?
Aspergillus fumigatus
This is particularly associated with prolonged ABx use - if ABx hasn’t worked it may have a fungal cause
Also common in severely immunosuppressed patients, eg on chemotherapy
Which type of LRTI is more common in people who have had a BM transplant?
CMV
Which pneumonia pathogens can be tested for in urine?
Legionella
S pneumoniae
Which type of atypical pneumonia are those who work around farm animals at increased relative risk of?
Coxiella burnetti
What colour does gram stain appear with gram pos/gram neg bacteria?
Gram pos: blue
Gram neg: pink
What is the treatment for mild-moderate pneumonia?
Amoxicilin
What is the first line treatment for HAP?
Ciprofloxacin +/- vancomycin
If severe: Tazocin (same thing as pip-tazo (piperacilin + tazobactam) + vanc
Aspiration: tazocin + Metronidazole
What type of antobiotic is coxiella burnetti (Q fever) pneumonia sensitive to?
Macrolides
How will CXR appear in bronchitis?
Normal
Which pathogen is the most likely cause of a post-influenza pneumonia?
S aureus
Which pneumonia-causing pathogen is associated with smoking?
M catarrhalis
Which pathogen is associated with the cause of pneumonia in the alcohol-dependent and the elderly?
Klebsiella
Which pathogen is associated with the cause of pneumonia in patients with pre-existing COPD?
Haemophilus influenza
Which type of pneumonia gives a positive cold agglutinin test?
Mycoplasma pneumonia
Which type of pneumonia may present with erythema multiforme?
Mycoplasma pneumonia
Which stain can be used to detect PCP, and what shape would the organisms appear?
Silver stain (Gomari’s methamine silver)
Boat-shaped organisms
May also show “flying saucer cysts”
Co-trimoxazole can be used to treat PCP
How can chlamydia pneumonia be diagnosed?
PCR of TWAR (Taiwan acute respiratory agent) agent
How can PCP be diagnosed in the lab?
Gomori’s methanamine
silver stain in cytology lab
Shows boat-shaped/flying saucer shaped organisms
Pneumocystis Jirovecii is a yeast like fungus
What are some examples of typical and atypical causes of CAP
Typical:
Strep pnuemoniae
Haemophilis influenzae
Moraxella catarrhalis
Atypical:
Legionella Pneumophila (Causes hyponatreamia) Mycoplasma pneumoniae (Causes erythema multiforme, positive cold agglutinin test) Chlamydia pneumoniae
Some examples of HAP
E.coli
Klebsiella
MRSA
Pseudomonas
Order of prevelance
Which types of pneumonia pathogens cause cavitating lesions
Klebsiella
Staph aureus
TB
What can be used to treat PCP?
Co-trimoxazole (sulfomethoxazole-trimethoprim)
